difference between have to and should? when we use?

Should (past form of shall) Often used in auxiliary functions to express an opinion, suggestion, preference, or idea: You should rest at home today. I should take a bus this time. He should be more thoughtful in the decision-making process. Used to express that you wish something had happened but it didn't or couldn't (should + have + past participle) : You should have seen it. It was really beautiful. I should have completed it earlier to meet the deadline. We should have visited the place on the way. Used to ask for someone's opinion: What should we do now? Should we continue our meeting? Should we go this way? Where should we go this summer? Used to say something expected or correct: There should be an old city hall building here. Everybody should arrive by 6 p.m. We should be there this evening.

Have to" is used to express certainty, necessity, and obligation. Examples: This answer has to be correct.  certainty The soup has to be stirred continuously to prevent burning.  necessity They have to leave early.  obligation